The present invention relates to an apparatus and method for removing oxides from dross and reclaiming solder from the dross.
A wave soldering machine is designed to automatically solder electronic components to a printed circuit board. Typically, a conventional wave soldering machine includes a solder reservoir within which a supply of molten solder is kept at a preset temperature. At least one solder wave nozzle is arranged in the solder reservoir, and a pump is associated with the solder wave nozzle to pump the molten solder upwardly through the solder wave nozzle to produce a solder wave. The printed circuit board is passed over the top of the solder wave to skim its surface. During this passage, conductive solder joints are formed between electronic components and the printed circuit board.
A problem associated with such a wave soldering machine is that dross, typically oxides of tin and lead, is generated wherever molten solder is exposed to atmospheric air. Dross generation not only adds considerably to the cost of the wave soldering process due to the value of lost solder, but also is detrimental to the quality of the resulting solder joint.
Various attempts have been made to remove dross and reclaim solder from the dross. For example, U.S. Pat. No. 6,235,208 teaches the use of an oxides separating agent such as rice bran adapted to facilitate removal of dross or tin and lead oxides. A netted container is partly dipped into a pool of molten solder which is, in turn, held in a solder reservoir. Dross present on the surface of the molten solder is transported from the solder reservoir to the netted container. A spoon is employed to spread a suitable oxide separating agent over the dross. The netted container is repeatedly dipped into and lifted up from the pool of molten solder. As a result of this procedure, tin and lead oxides are left in the container while reclaimed solder is returned to the solder reservoir. It is to be understood that dross consists of pockets of good solder which are surrounded by a crust-like envelope of tin and lead oxides. Liquid solder can escape from the oxide crust when the dross is continuously heated to a sufficient temperature. In this procedure, however, dross is cooled when the netted container is lifted up from the pool of molten solder. Thus, this procedure is not satisfactory.
Accordingly, it is an object of the present invention to provide a solder dross removal apparatus and method which can efficiently and effectively remove oxides from dross and reclaim solder from the dross.